The Council on American-Islamic Relations (CAIR) has called for increased police protection after three mosques in California received threatening letters in the last week.
The mosques in Long Beach, Claremont and San Jose have all received a letter saying that President-elect Trump will do to Muslims "what Hitler did to the Jews" - a reference to the mass genocide carried out by the Nazis during the Holocaust.
The latter, published by US political website The Hill, reads as follows:
"To the children of Satan, You Muslims are a vile and filthy people. Your mothers are whores and your fathers are dogs. You are evil. You worship the devil. But your day of reckoning has arrived.
There’s a new sheriff in town — President Donald Trump. He’s going to cleanse America and make it shine again. And he’s going to start with you Muslims. He’s going to do to you Muslims what Hitler did to the Jews. You Muslims would be wise to pack your bags and get out of Dodge.
"This is a great time for patriotic Americans. Love live President Trump and God bless the USA."
The CAIR has requested increased protection from police in California and demanded an investigation into the letter.